Respirators are frequently worn by people working in areas where the air may be contaminated with toxic or noxious substances such as particulates, gases and vapors. For example, the air in a sanding or grinding area may contain airborne particulates, the air in a painting area may contain droplets of paint or solvent vapors, and the air in a welding area may contain harmful particles or fumes.
The respirator may filter the air or it may provide a supply of uncontaminated air. A positive pressure respirator has a source of clean air brought into the mask under positive pressure, giving a higher pressure inside the mask of the respirator than in the surrounding ambient air. The source of clean air may include blowing or pulling ambient air through a filter or it may include bringing clean air in from an external source,
A positive pressure respirator usually employs a breathing tube to direct the clean air into the breathing zone of the respirator. Because the breathing tube is a source of clean air, the security of the attachment of the breathing tube to the headgear is important. Potential hazards include objects that may catch on the latch, thereby leading to a risk that the tube becomes separated from the respirator.
Various governmental agencies and industry organizations have established regulations specifying standards that must be met by this connection under certain use conditions. For example, the European Committee for Standardization requires that the connection must withstand a pulling force of 25 kilograms, or approximately 56 lbs. of pressure (CEN Type 3).
A common attachment method currently in use with respiratory devices involves a rigid cylindrical fitting projecting from the headgear to which the breathing tube is attached. This attachment typically employs a rigid cylindrical fitting on the end of the breathing tube. For example, U.S. Pat. No. 4,996,981 describes a respiratory device in which the device includes an aperture or orifice into which a hose is fitted in sealing relation. Other similar examples are disclosed in U.S. Pat. Nos. 3,736,927; 3,963,021; and 4,676,236. Similarly, U.S. Pat. No. 3,921,223 describes a rearwardly extending nipple that is designed to engage the end of a tube, which is made of flexible plastic or rubber material. The attachment fitting or nipple may also be ribbed or tapered.
Various clamping devices have been used to provide a more secure attachment of the breathing tube to the respirator. For example, in U.S. Pat. No. 5,549,104 a breathing tube is secured in a sleeve by means of a clamp that encircles the sleeve overlying an end portion of the tube. Other clamps have also been used, including pinch clamps, clamps tightened with a screwdriver, and clamps tightened with a thumbscrew. Compression fittings tightened by a threaded retainer have also been used.